Sequence Of Short Pulses Research Articles

Multi-dimensional chaos initiated by short pulses in non-autonomous radio-physical generator

A non-autonomous model of the Anishchenko–Astakhov generator in the regime of periodic and chaotic self-oscillations is considered. A periodic sequence of short pulses is considered as an external force. It is shown that the synchronization picture is close in structure to the classical synchronization picture observed in a two-dimensional system, but the pulse action leads to the excitation of chaotic oscillations, including those characterized by a different spectrum of Lyapunov exponents. In particular, it is shown appearance of hyperchaos and chaos with additional close to zero Lyapunov exponent. Phenomenological scenarios for the development of multi-dimensional chaos related to destruction of two-frequency tori are described. Hyperchaos is formed via hierarchy of discrete Shilnikov attractors arise as a result of sequence of Neimark-Sacker bifurcations. Chaos with additional close to zero Lyapunov exponent occurs as impact of saddle tori appeared via sequence of torus-doubling bifurcations.

High-fidelity quantum gates via optimizing short pulse sequences in three-level systems

We propose a robust and high-fidelity scheme for realizing universal quantum gates by optimizing short pulse sequences in a three-level system. To alleviate the sensitivity to the errors, we recombine all elements of error matrices to construct a cost function with three types of weight factors. The modulation parameters are obtained by searching for the minimum value of this cost function. The purposes of introducing the weight factors are to reduce the detrimental impact of high-order error matrices, suppress population leakage to the third state, correct the operational error in the qubit space, and optimize the total pulse area of short pulse sequences. The results demonstrate that the optimized sequences exhibit strong robustness against errors and effectively reduce the total pulse area. Therefore, this work presents a valuable method for achieving exceptional robustness and high speed in quantum computations.

Thermal Cues Composed of Sequences of Pulses for Transferring Data via a Haptic Thermal Interface.

This research study is the preliminary phase of an effort to develop a generic data transfer method via human haptic thermal sensation (i.e., a coded language such as Morse or Braille). For the method to be effective, it must include a large variety of short, recognizable cues. Hence, we propose the concept of cues based on sequences of thermal pulses: combinations of warm and cool pulses with several levels of intensity. The objective of this study was to determine the feasibility of basing a generic data transfer method on haptic thermal cues using sequences of short pulses. The research included defining the basic characteristics of the stimuli parameters and developing practical methods for generating and measuring them. Several patterns of different sequences were designed considering the relevant data known to date and improved by implementing new insights acquired throughout the tests that were conducted. The final thermal cues presented to the participants were sensed by touch and clearly recognized. The results of this study indicate that developing this new method is feasible and that it could be applicable in various scenarios. In addition, the low impact measured on the user's skin temperature represents an inherent advantage for future implementation. This report presents promising findings and offers insights for further investigations.

Generation of dual and quad-optical frequency combs in the injected radiation free mode-locked frequency-shifted feedback laser

The results of an optoelectronic system—frequency-shifted feedback (FSF) laser experimental examination are presented. The considered FSF laser is seeded only with optical amplifier spontaneous emission (ASE) and operates in the mode-locked regime, whereby the output radiation is sequence of short pulses with a repetition rate determined by the delay time in its optical feedback circuit. In the frequency domain, the spectrum of such a pulse sequence is an optical frequency comb (OFC). These OFCs we call initial. We consider the possibility of tunable acousto-optic (AO) dual and quad-comb frequency spacing downconversion in the FSF laser seeded with ASE and operating in the mode-locked regime. The examined system applies a single frequency shifting loop with single AO tunable filter as the frequency shifter that is fed with several radio frequency signals simultaneously. The initial OFCs with frequency spacing of about 6.5 MHz may be obtained in the wide spectral range and their width, envelope shape and position in the optical spectrum may be tuned. The dual-combs are obtained with a pair of initial OFCs aroused by two various ultrasound waves in the acousto-optic tunable filter (AOTF). The dual-combs frequency spacing is determined by the frequency difference of the signals applied to the AOTF piezoelectric transducer and can be tuned simply. The quad-combs are obtained with three initial OFCs, forming a pair of dual-combs, appearing when three ultrasound frequencies feed the AOTF transducer. The quad-combs frequency spacing is defined by the difference between the frequency spacing of dual-combs. Quad-combs with more than 5000 spectral lines and tunable frequency spacing are observed. The successive frequency downconversion gives the possibility to reduce the OFC frequency spacing form several MHz for initial OFC to tens of kHz for quad-combs.Graphical abstract

SIMPLE PULSE MICROWAVE WAVEGUIDE CALORIMETER WITH TEMPERATURE SENSOR LM 35

The paper presents the construction of a storage-type waveguide calorimeter designed to measure the energy of a sequence of short microwave pulses. The radiation is absorbed by water or ethanol, then the temperature increase is recorded by the LM 35 sensor. When using 14 cm3 of water, the energy measurement range is 3…88 J, and when using ethanol 1.3…40 J. The calorimeter is simple, cheap, and reliable.

Approximate analytical expressions for the Carr–Purcell–Meiboom–Gill sequences: Decay rates and modulation zeros of the echo train and the relation between the [formula omitted] and [formula omitted] relaxation times

Methods of multi-pulse sequences are widely used in magnetic resonance to study the local properties of magnetic particles and to increase the lifetime of spin coherence. Imperfect refocusing pulses lead to non-exponential signal decay due to the contribution of the coherence pathways in which T1 and T2 relaxation segments are mixed. Here, we present analytical approximations for echoes generated in the Carr-Purcell-Meiboom-Gill (CPMG) sequence. They provide simple expressions for the leading terms of the echo train decay and allow the relaxation times to be estimated for sequences with a relatively small number of pulses. For a given refocusing angle α, the decay times for the fixed phase and alternating phase CPMG sequences can be approximated as (T2-1+T1-1)/2 and T2O, respectively. The ability to estimate relaxation times from short pulse sequences can reduce the acquisition time, which is essential for the methods used in magnetic resonance imaging. In the case of a CPMG sequence with the fixed phase, the relaxation times can also be obtained from the points in the sequence at which the echo changes sign. Numerical comparison of the exact and approximate expressions shows the practical limits of the analytical formulas obtained. It is also shown that a double echo sequence in which the interval between the first two pulses is not equal to half the interval of the subsequent refocusing pulses provides the same information as two separate CPMG (or CP) sequences with fixed and alternating phases of the refocusing pulses. In addition, the two double-echo sequences differ in the parity of the number of intervals with longitudinal magnetization evolution (relaxation), i.e. the echo in one sequence is formed only from those coherence pathways that have an even number of intervals with longitudinal magnetization evolution, while the other sequence has an odd number of such intervals.

Generation of Short Pulses by Filtering Phase-Modulated CW Laser Radiation

A method for generating short pulses with a high repetition rate is proposed. It is based on periodic modulation of the radiation phase of a CW laser and subsequent filtering through a narrow-band frequency filter. At the output of the filter, a sequence of short pulses is generated with a period equal to half the modulation period. In the case of a resonant filter using atoms, ions or molecules with a narrow absorption line, the appearance of pulses can be explained by constructive interference of the incident radiation with radiation coherently scattered by resonant particles. An alternative explanation of the pulse generation in the general case, when frequency filters operating on other principles are used, is based on the interference of the spectral components remaining after filtering. The method can be applied for time division multiplexing to transmit digital information through a single channel at high speed. The advantage of the proposed method is the use of phase modulation (not strictly periodic), integrated with frequency filtering to generate pulses and encode information simultaneously in one circuit, while in other known methods, information is introduced into a sequence of regularly generated pulses using additional amplitude modulation.

16.3 W Peak-Power Pulsed All-Diode Laser Based Multi-Wavelength Master-Oscillator Power-Amplifier System at 964 nm

An all-diode laser-based master oscillator power amplifier (MOPA) configuration for the generation of ns-pulses with high peak power, stable wavelength and small spectral line width is presented. The MOPA emits alternating at two wavelengths in the spectral range between 964 nm and 968 nm, suitable for the detection of water vapor by absorption spectroscopy. The monolithic master oscillator (MO) consists of two slightly detuned distributed feedback laser branches, whose emission is combined in a Y-coupler. The two emission wavelengths can be adjusted by varying the current or temperature to an absorption line and to a non-absorbing region. The power amplifier (PA) consists of a ridge-waveguide (RW) section and a tapered section, monolithically integrated within one chip. The RW section of the PA acts as an optical gate and converts the continuous wave input beam emitted by the MO into a sequence of short optical pulses, which are subsequently amplified by the tapered section to boost the output power. For a pulse width of 8 ns, a peak power of 16.3 W and a side mode suppression ratio of more than 37 dB are achieved at a repetition rate of 25 kHz. The measured spectral width of 10 pm, i.e., 0.1 cm−1, is limited by the resolution of the optical spectrum analyzer. The generated pulses emitting alternating at two wavelengths can be utilized in a differential absorption light detection and ranging system.

Resonance Fabry–Perot interferometer as instrument for investigation of fine and hyperfine mode structure of free electron lasers

Free electron lasers usually emit periodic sequences of short pulses, which are parts of pulses circulating inside an optical cavity. Due to the laser nature of the radiation, the output pulses generated by the same intra-cavity pulse are a priori coherent with each other. Under certain technical conditions, different intra-cavity pulses can be coherent too. The coherence of intra-cavity pulses gives rise to a fine structure of the laser emission spectrum, and the coherence of output pulses from one intra-cavity pulse gives rise to a hyperfine mode structure. The article describes a special device, the resonance Fabry–Perot interferometer, and methods for panoramic frequency measurements of the mode composition of radiation with a resolution of up to 5⋅ 10−8 and for practically unlimited-resolution time-domain measurements of the monochromaticity of lines of hyperfine structure. With this device, it was shown that there is no fine structure in the Novosibirsk free electron laser (NovoFEL), and its hyperfine structure was measured in detail. The measurement of hyperfine structure of an FEL was carried out for the first time. It is shown that under certain conditions, NovoFEL operates either in the generation regime of one Laguerre-Gaussian supermode or in the regime of several transverse supermodes. The measured relative linewidth of the NovoFEL hyperfine mode structure, defined by technical factors, is 2.2 × 10−8, which is about two orders of magnitude larger than its absolute physical quantum limit.

THE FORMATION METHOD OF COMPLEX SIGNALS ENSEMBLES BY FREQUENCY FILTRATION OF PSEUDO-RANDOM SEQUENCES WITH LOW INTERACTION IN THE TIME DOMAIN

Context. The problem of forming complex signal ensembles on the basis of frequency band filtering and research of their properties is considered. The object of research is the process of synthesis of signal ensembles based on frequency filtering of pseudo-random sequences of short video pulses with low interaction in the time domain.Objective. It is to form complex signal ensembles with satisfactory values of intercorrelation properties, which are close to the signals with minimal energy interaction. Method. The results of the application of forming complex signal ensembles method by frequency filtering of pseudo-random sequences with low interaction in the time domain are presented. As a result of the spectral band selection of the studied pseudorandom short video pulse sequences due to the use of bandpass filters based on the Chebyshev filter of the first kind, new samples of sequences with spectrum restriction are obtained. By applying intercorrelation analysis to the obtained sequence samples, the values of the maximum emissions of the side lobes of the cross-correlation functions (CCF) for all possible signal pairs are estimated. If the values of the maximum emissions of the side lobes of the CCF signals exceed the limit values, the sequence of the analyzed pair with a smaller value of the number of pulses is removed from the ensemble. In case of satisfactory value – the received signals are accepted for the signal ensemble formation with the minimum power interaction. Thus, a new set of values of the maximum emissions of the side lobes of the CCF is formed. This approach increases the number of signals in ensembles with satisfactory values of statistical characteristics with limited signal spectrum width, and the correlation properties of such sequences approach the signals with minimal energy interaction, which reduces the level of multiple access interference. As a result, complex signal ensembles obtained by frequency filtering should be used in cognitive radio systems with code division multiplexing.Results. Based on the software implementation of the method of forming complex signal ensembles by frequency filtering of pseudo-random sequences with low interaction in the time domain, signals with satisfactory values of statistical characteristics with limited signal spectrum width with intercorrelation properties close to signals with minimal energy interaction and higher ensemble volume were selected.Conclusions. The application of frequency filtering to pseudo-random sequences of short video pulses with a low level of crosscorrelation allows to obtain complex signal ensembles, which will be similar in correlation properties to sequences with minimal energy interaction. It will reduce the level of multiple access interference. The analysis revealed that the use of frequency filtering of sequences will slightly worsen the mutual correlation properties of signals, possibly due to suboptimal synthesis of values of maximum emission levels of side lobes of CCF signals, but, nevertheless, it is possible to use such signals in modern cognitive systems radio access multiple access with code division multiplexing.

Multi-Purpose Microwave Biosensor Based on Signal Encoding Technique and Microfluidics for Improved Sensitivity

In this paper, a microwave biosensor with unprecedented sensitivity based on encoded pulse propagation and microfluidics is theoretically investigated and experimentally demonstrated. The structure consists of a double-spiral transmission line on FR4 substrate electromagnetically coupled to a copper coiled capillary tube above it. The working principle for improved sensitivity consists of propagating an encoded sequence of short pulses (Walsh-Hadamard spreading code with variable temporal length) in a recirculating manner so that the pulses are deformed both due to dispersive and time-delay effects. Once the recirculation is finished, the energy of the code at the sensor output is calculated, providing an indicator directly related with the analyte concentration. The experimental results demonstrate the improved sensitivity of this sensor approach for the case of glucose with 2.9 mg/ml resolution. Furthermore, we demonstrate the potential of this technology as a sensor platform by investigating other chemical compounds such as isopropyl alcohol (IPA) and acetone with a sensitivity of 20% of the volume. Finally, the outstanding performance, both in terms of accuracy and sensitivity, situates the present multi-purpose approach within the state-of-the-art of microwave (bio)chemical sensors.

Comparing rapid short-pulse to tone burst sonication sequences for focused ultrasound and microbubble-mediated blood-brain barrier permeability enhancement

ObjectiveTranscranial focused ultrasound and microbubble (FUS + MB) exposure enables targeted, noninvasive drug delivery to the brain. Given the protective nature of the blood-brain barrier (BBB), the development of sonication strategies that maximize therapeutic efficacy while minimizing the risk of tissue damage are essential. This work aimed to compare the safety of 10 ms tone bursts, widely used in the field, to a recently described rapid short-pulse (RaSP) sequence, while accounting for drug delivery potential. Materials and methodsForty-one male wild-type mice received FUS + MB exposure (1.78 MHz driving frequency; 0.5 Hz burst repetition frequency; 250 s duration; 40 μl/kg Definity) at a range of fixed pressure amplitudes. A RaSP sequence (13 five-cycle pulses/10 ms burst) was compared to 10 ms tone bursts (B10). For animals in cohort #1 (n = 26), T1 mapping was used to quantify gadobutrol extravasation. Three targets, temporarily separated by 10 min, were sonicated in each brain to compare the time dependence of BBB permeability enhancement between sequences. Red blood cell (RBC) extravasation was quantified to assess vascular damage. For animals in cohort #2 (n = 18), a single target was sonicated per brain. BBB permeability enhancement was compared between sequences by T1 mapping and the extravasation of a 3 kDa fluorescent dextran. ResultsAt a peak negative pressure of 400 kPa, the B10 sequence produced an order of magnitude greater gadobutrol and dextran extravasation compared to RaSP (p < 0.01). When accounting for BBB permeability enhancement magnitude, as measure by T1 mapping, no differences were observed between sequences in the pattern of dextran or albumin extravasation in tissue sections; however, the frequency of RBC extravasation was found to be 5 times greater with the RaSP sequence (p = 0.02). At pressure amplitudes resulting in similar levels of gadobutrol extravasation, no significant differences were observed in the time dependence of BBB permeability enhancement between sequences. ConclusionWhen accounting for the magnitude of BBB permeability enhancement, and thus the potential for drug delivery, the RaSP sequence tested here did not produce measurable improvements over the B10 sequence and may present an increased risk of vascular damage.

Imaging With Therapeutic Acoustic Wavelets-Short Pulses Enable Acoustic Localization When Time of Arrival is Combined With Delay and Sum.

Passive acoustic mapping (PAM) is an algorithm that reconstructs the location of acoustic sources using an array of receivers. This technique can monitor therapeutic ultrasound procedures to confirm the spatial distribution and amount of microbubble activity induced. Current PAM algorithms have an excellent lateral resolution but have a poor axial resolution, making it difficult to distinguish acoustic sources within the ultrasound beams. With recent studies demonstrating that short-length and low-pressure pulses-acoustic wavelets-have the therapeutic function, we hypothesized that the axial resolution could be improved with a quasi-pulse-echo approach and that the resolution improvement would depend on the wavelet's pulse length. This article describes an algorithm that resolves acoustic sources axially using time of flight and laterally using delay-and-sum beamforming, which we named axial temporal position PAM (ATP-PAM). The algorithm accommodates a rapid short pulse (RaSP) sequence that can safely deliver drugs across the blood-brain barrier. We developed our algorithm with simulations (k-wave) and in vitro experiments for one-, two-, and five-cycle pulses, comparing our resolution against that of two current PAM algorithms. We then tested ATP-PAM in vivo and evaluated whether the reconstructed acoustic sources mapped to drug delivery within the brain. In simulations and in vitro, ATP-PAM had an improved resolution for all pulse lengths tested. In vivo, experiments in mice indicated that ATP-PAM could be used to target and monitor drug delivery into the brain. With acoustic wavelets and time of flight, ATP-PAM can locate acoustic sources with a vastly improved spatial resolution.

A New Noise-Suppression Algorithm for Transient Thermal Analysis in Semiconductors Over Pulse Superposition

This article introduces a new measurement method for noise suppression in transient thermal analysis (TTA), which is used to measure the transient thermal impedance of power semiconductors and LEDs. An additional short pulse sequence is added to the standard TTA measurement procedure. The thermal response of this additional sequence is converted into the original single-pulse response of standard TTA by superposition of previous pulses in the sequence. Applying this method, the noise before 1 ms can be significantly reduced without averaging over multiple measurement repetitions that would increase the measurement time accordingly. The noise reduction for times below 1 ms is important to resolve the thermal resistance layers close to the junction of a semiconductor. The measurement method and data analysis algorithm are developed for TTA measurements, but the principle is suitable for all linear time-invariant (LTI) systems where the system response is measured over several time decades. The algorithm was evaluated on simulated and experimental data of a power LED. With an additional sequence of only 100 ms, a signal-to-noise ratio (SNR) improvement of 15.1 dB for simulated data and 14.7 dB for experimental data was achieved. This is equivalent to averaging over 30 repetitions in the standard TTA procedure. Therefore, the new method achieves a reduction of measurement time of 97% for applications where low noise levels are required for times below 1 ms.

Detachment plasma achieved based on active temperature feedback system in EAST

The infrared (IR) thermography diagnostic has recently been upgraded to achieve real-time temperature measurement and feedback capability in the experimental advanced superconducting tokamak (EAST). A new control and data acquisition program for IR camera is developed with online temperature calibration and compensation. Reflective memory (RFM) is configured in the data acquisition system for real-time data transmission to the plasma control system (PCS). Based on the upgraded IR thermography diagnostic, detachment plasma has been achieved for the first time in EAST with active temperature feedback. The divertor impurity seeding system is used to inject a sequence of short neon impurity pulses with 50% D2 to increase the edge radiation of the plasma particles. The temperature of the divertor target plates decreases to the preset target value and the divertor detachment has been realized with no serious reduction of plasma stored energy and confinement observed in the temperature feedback control phase. As a new feedback control method, the IR temperature feedback control shows great application prospects for the temperature and heat flux control of the first wall components in future long pulse operation of EAST.

High-resolution in vivo MR-STAT using a matrix-free and parallelized reconstruction algorithm.

MR‐STAT is a recently proposed framework that allows the reconstruction of multiple quantitative parameter maps from a single short scan by performing spatial localisation and parameter estimation on the time‐domain data simultaneously, without relying on the fast Fourier transform (FFT). To do this at high resolution, specialized algorithms are required to solve the underlying large‐scale nonlinear optimisation problem. We propose a matrix‐free and parallelized inexact Gauss–Newton based reconstruction algorithm for this purpose. The proposed algorithm is implemented on a high‐performance computing cluster and is demonstrated to be able to generate high‐resolution (1 mm × 1 mm in‐plane resolution) quantitative parameter maps in simulation, phantom, and in vivo brain experiments. Reconstructed T1 and T2 values for the gel phantoms are in agreement with results from gold standard measurements and, for the in vivo experiments, the quantitative values show good agreement with literature values. In all experiments, short pulse sequences with robust Cartesian sampling are used, for which MR fingerprinting reconstructions are shown to fail.

Modelling of dual-port computing operations of a phase-change memory cell

The general model of a phase-change memory (PCM) cell is very complex due to electrical property, thermal transfer and crystal growth. In this paper the general model is equivalent to an RC circuit, via which the dependence of the cell resistance on the number of pulses (Set or Reset) was investigated. Moreover, as for dual-port asynchronous operations of a pore-type PCM cell, a double-capacitor-based cell model was proposed. By simulation on the model we verified feasibility of the cell’s logic and arithmetic operations. In addition, the simulation results of addition and subtraction show that the resistance changes linearly with a short pulse sequence.

Ultrasound Intra Body Multi Node Communication System for Bioelectronic Medicine.

The coming years may see the advent of distributed implantable devices to support bioelectronic medicinal treatments. Communication between implantable components and between deep implants and the outside world can be challenging. Percutaneous wired connectivity is undesirable and both radiofrequency and optical methods are limited by tissue absorption and power safety limits. As such, there is a significant potential niche for ultrasound communications in this domain. In this paper, we present the design and testing of a reliable and efficient ultrasonic communication telemetry scheme using piezoelectric transducers that operate at 320 kHz frequency. A key challenge results from the multi-propagation path effect. Therefore, we present a method, using short pulse sequences with relaxation intervals. To counter an increasing bit, and thus packet, error rate with distance, we have incorporated an error correction encoding scheme. We then demonstrate how the communication scheme can scale to a network of implantable devices. We demonstrate that we can achieve an effective, error-free, data rate of 0.6 kbps, which is sufficient for low data rate bioelectronic medicine applications. Transmission can be achieved at an energy cost of 642 nJ per bit data packet using on/off power cycling in the electronics.

Metal plate deformation under magnetic field pulse of complex shape

A dynamic deformation of sheet magnetic and nonmagnetic metal workpieces under a combination of a slowly varying primary magnetic field and a sequence of short magnetic field pulses with the opposite polarity is studied. This regime corresponds to backward electromagnetic forming. A fast motion of the workpiece induces an additional electromotive force in a discharge circuit and substantially alters a shape of the current pulse in an inductor. During the short opposite pulses, the Lorentz and magnetization components of the magnetic pressure on the magnetic workpiece demonstrate an unusual behavior, that is, the Lorentz pressure is attractive and the magnetization one is predominantly repulsive relative to the inductor. This phenomenon is discussed in terms of a two-dimensional axisymmetric problem.

Feasibility of fast brain diffusion MRI to quantify white matter injury in pediatric hydrocephalus.

Traditionally, diffusion MRI (dMRI) has been performed in parallel with high-resolution conventional MRI, which requires long scan times and may require sedation or general anesthesia in infants and young children. Conversely, fast brain MRI permits image acquisition without the need for sedation, although its short pulse sequences, susceptibility to motion artifact, and contrast resolution have limited its use to assessing ventricular size or major structural variations. Here, the authors demonstrate the feasibility of leveraging a 3-direction fast brain MRI protocol to obtain reliable dMRI measures. Fast brain MRI with 3-direction dMRI was performed in infants and children before and after hydrocephalus treatment. Regions of interest in the posterior limbs of the internal capsules (PLICs) and the genu of the corpus callosum (gCC) were drawn on diffusion-weighted images, and mean diffusivity (MD) data were extracted. Ventricular size was determined by the frontal occipital horn ratio (FOHR). Differences between and within groups pre- and posttreatment, and FOHR-MD correlations were assessed. Of 40 patients who met inclusion criteria (median age 27.5 months), 15 (37.5%), 17 (42.5%), and 8 (20.0%) had posthemorrhagic hydrocephalus (PHH), congenital hydrocephalus (CH), or no intracranial abnormality (controls), respectively. A hydrocephalus group included both PHH and CH patients. Prior to treatment, the FOHR (p < 0.001) and PLIC MD (p = 0.027) were greater in the hydrocephalus group than in the controls. While the mean gCC MD in the hydrocephalus group (1.10 × 10-3 mm2/sec) was higher than that of the control group (0.98), the difference was not significant (p = 0.135). Following a median follow-up duration of 14 months, decreases in FOHR, PLIC MD, and gCC MD were observed in the hydrocephalus group and were similar to those in the control group (p = 0.107, p = 0.702, and p = 0.169, respectively). There were no correlations identified between FOHR and MDs at either time point. The utility of fast brain MRI can be extended beyond anatomical assessments to obtain dMRI measures. A reduction in PLIC and gCC MD to levels similar to those of controls was observed within 14 months following shunt surgery for hydrocephalus in PHH and CH infants. Further studies are required to assess the role of fast brain dMRI for assessing clinical outcomes in pediatric hydrocephalus patients.